C# Microsoft Exchange Web服务-带有附件的邮件不'；收不到收件人

我对Microsoft Exchange Web服务有问题。我尝试通过邮件发送表单信息。这很好用。 如果我添加了附件，邮件将无法送达收件人。没有任何错误消息或类似的东西

（我将Webservice作为nuget包集成到asp.net核心（模型视图控制器）项目中。）

有人能帮我吗

致意

JuRi-2020

 public void sendMail(string bodyMessage, ComplainData complaint, string language, string path){ 
        ExchangeService service = new ExchangeService(ExchangeVersion.Exchange2010_SP2);
        service.UseDefaultCredentials = true;
        service.Url = new Uri("sample");
        EmailMessage message = new EmailMessage(service);

        switch (language)
        {
            case "de":
                message.Subject = $"Reklamation von {complaint.CompanyName} wurde übermittelt.";
                message.Body = bodyMessage;
                message.Body.BodyType = BodyType.HTML;
                message.ToRecipients.Add("mail");
                if (path != null)
                {
                    message.Attachments.AddFileAttachment(path);
                }

                try
                {
                    message.Send();
                }
                catch
                {
                    this.successful = false;
                }
                break;}          }